This invention relates to a rigid endoscope optical system, especially to a stereoscopic rigid endoscope system.
Conventionally, the stereoscopic endoscope is known as described in, for example, Japanese Laid-Open Publication No. 7-261099, Japanese Laid-Open Publication No. 8-122665, and Japanese Laid-Open Publication No. 11-6967.
In endoscopic surgery, both wide angle and magnified images are required. The wide angle image is used for finding an organ, a disease, or a treatment tool, while the magnified image is used for treatment. A conventional rigid endoscope usually has only one observation optical system. When a wide angle objective lens is arranged in the optical system, above-mentioned need is carried out by using one of following methods.
(A) Changing distance to the object
(B) Using optical zoom function on the side of TV camera system connected to the optical System
On the one hand, endoscopic robot surgery system has been developed recently. In this case, surgical treatment tools and an endoscope are operated remotely by a surgeon. Since such robot enables precise surgical treatment, surgeons require endoscopes to have better images with higher magnification and higher resolution at the time of treatment.
When either of the above methods (A) or (B) are used in endoscopic robot surgery in order to magnify the image of a object, some problems arise.
In method (A), if a rigid endoscope is brought close to a target object, interference between the endoscope and treatment tools will pose a problem. Therefore, the field angle of view should be narrow at the time of a treatment to get both high magnification and long working distance(WD). However, if an objective lens is made into a narrow angle, the wide angle image for finding will not be obtained.
In method (B), a combination of a wide angle rigid endoscope and a camera system with optical zoom function enables both wide image and high magnification image. But the high magnification image has worse image quality than the wide image because the point spread property of a rigid endoscope is fixed and the final point spread property at the imaging surface in the camera system is magnified according to the optical zoom state in the camera system. That is, the longer focal length of the zoom optics makes the final point spread property worse. This deterioration of image quality in a high magnification state cannot be tolerated for precise treatment.
Moreover, in the endoscopic robot surgery system, a stereoscopic rigid endoscope system is preferred in order to obtain a depth perception. In this case, however, there are the following problems in addition to the above problems.
First, it is more difficult to get good image quality than in the case of a two-dimensional image (2D). In the stereo endoscope, it is necessary to transmit the right and left images within the space of the limited insertion part. In this case, the image quality of the stereo endoscope will be degraded more than in the case of 2D.
Second it is difficult to add a zoom function in the stereo endoscope system, while keeping the right and left optical conditions satisfied.
In view of the foregoing disadvantages inherent in the known types of prior art, the present invention solves the above-mentioned problems. Thus, it is an object of the present invention to provide a rigid endoscope optical system which enables both the wide angle image for finding an organ or treatment tools and the high resolution image used for a precise treatment. In addition, to provide the suitable optical system for a stereo endoscope system.
The first rigid endoscope optical system of this invention which attains the above objectives comprises a primary objective optical system, a secondary objective optical system with a wider field of view than the primary objective optical system, and a relay optical system which transmits images or pupils made by these objective optical systems.
As constructed as described above, it is possible to obtain both a wide angle image used for finding and a narrow angle image with high resolution used for the precise treatment. Since the present invention uses a common relay optical system, and the relay optical system has a larger outer diameter, the relay optical system has lower optical performance requirements and fewer manufacturing errors than the case of using respective relay optical systems which correspond to the primary and the secondary objective optical systems. Therefore, the image quality deterioration after assembling is small. Moreover, the number of lenses in the relay optical system is reduced and the larger outer diameter of lenses increases manufacturing workability. Therefore, the present invention decreases the total cost of the relay optical system.
It is desirable that both the primary and secondary objective optical systems have nearly the same direction of view regardless of direct or oblique direction of view.
In the case of getting an oblique direction of view, it is desirable that both the primary and the secondary objective optical systems share a prism unit to get an oblique field direction. In the case of using respective prism units corresponding to the primary and secondary objective optical systems, it is difficult to reduce differences in direction of view between the primary and the secondary objective optical systems without precise adjustment. However, if the prism unit is made to share, the difference in direction of view will be made small without adjustments.
The present invention has two methods of transferring images made by the primary and the secondary objective optical systems. The first transfer method is to make real images just before the relay optical system and the second transfer method is to make pupils just before the relay optical system. In the first transfer method, the primary and the secondary objective optical systems are terminated by the real images and the relay optical system transmits the images to the final image plane of the relay optical systems. In this case, it is desirable that the primary and the secondary objective optical systems make real images on a nearly identical image plane and the images do not overlap on the image plane. If the images overlap on the image plane, it is impossible to separate the images completely after the relay optical system without partial lack of images. Accordingly, it is desirable to take such an arrangement.
In this case, it is desirable to have an optical means on the rear side of the relay optical system to separate the real images made by the relay optical system.
In the second transfer method, the primary and the secondary objective optical systems are terminated by the exit pupils and the relay optical system transmits the pupils to the exit pupil plane of the relay optical systems. In this case, it is desirable that the primary and the secondary objective optical systems make exit pupils on a nearly identical pupil plane and the pupils do not overlap on the pupil plane. The plane of the exit pupils made by the objective optical systems becomes an entrance pupil plane of the relay system. If the pupils overlap on the pupil plane, it is impossible to separate the pupils completely after the relay optical system without cross-talk (the image of a certain objective optical system mixes with the image of the other objective optical system). Accordingly, it is desirable to take such an arrangement.
In this case, it is desirable to have an optical means on the rear side of the relay optical system to separate the pupils made by the relay optical system.
In addition, it is desirable that the primary and the secondary objective optical systems form intermediate real images in their respective objective optical systems. If there were no optical systems for forming the intermediate real images, aberrations of each optical systems should be independently minimized. Therefore, the primary and the secondary objective optical systems and the relay optical system need to be independently optimized, respectively. If each objective optical system has no intermediate real images, it is difficult to correct aberrations and to get high quality images because of the few design variables in the lens constitution. Therefore, it is desirable that the primary and the secondary objective optical systems have intermediate real images, respectively.
Moreover, it is desirable that the primary objective optical system has a larger lens diameter than the secondary objective optical system. The primary objective optical system for treatment should be designed with high resolution. It is necessary for the primary objective optical system to have a large numerical aperture in order to get high resolution. Enlarging the lens diameter is one of the methods to get a large numerical aperture. Since the secondary objective optical system is used for finding, image quality of the secondary objective optical system is permissible even if it is somewhat bad.
Hereafter, the second rigid endoscope optical system of the present invention is explained. The second rigid endoscope optical system of the present invention comprises a primary objective optical system for stereoscopic observation which forms right and left images, a secondary objective optical system with wider field of view than the primary objective optical system for stereoscopic observation, and one relay optical system which transmits the images of these objective optical systems.
The primary objective optical system for stereoscopic observation is made to be able to get right and left images for stereoscopic observation. The secondary objective optical system is used for finding as in the first rigid endoscope optical system. All images made by the objective optical systems are transmitted by the relay optical system. Also in this case, the relay optical system has lower sensitivity against manufacturing error than the case of using respective relay optical systems which correspond to the primary and the secondary objective optical systems. Therefore, the image quality deterioration after assembling is small and total cost of the relay optical system is reduced as in the first rigid endoscope.
In this case, it is desirable that both the primary objective optical system for stereoscopic observation and the secondary objective optical system have nearly same direction of view regardless of direct or oblique direction of view. Especially in the stereoscopic observation, the direction of view of right and left images must be the same.
In the case of getting an oblique direction of view, it is desirable that both the primary stereoscopic and the secondary objective optical systems share a prism unit to get an oblique field direction. In the case of using respective prism units corresponding to the primary and secondary objective optical systems, it is difficult to reduce differences of the direction of view between the primary and the secondary objective optical systems without precise adjustment. However, if the prism unit is made to share, the difference in direction of view will be made small without adjusting. Especially since it is fatal if there a difference in direction of view between the right and left images, the shared prism is effective.
Moreover, the primary objective optical system for stereoscopic observation may have a right objective optical system and a left objective optical system independent of each other. Also both the first and the second image transfer methods are applicable in this embodiment. In the first transfer method, the right objective optical system, the left objective optical system, and the secondary objective optical system are terminated by the real images, and the relay optical system transmits the images to the final image plane of the relay optical systems. In this case, it is desirable that the left, the right, and the secondary objective optical systems make real images on a nearly identical image plane and the images do not overlap on the image plane. If the images overlap on the image plane, it is impossible to separate the images completely after the relay optical system without partial lack of images. Accordingly, it is desirable to take such an arrangement.
Also in this case, it is desirable to have an optical means on the rear side of the relay optical system to separate the real images made by the relay optical system.
In the second transfer method, the right, the left, and the secondary objective optical systems are terminated by the exit pupils and the relay optical system transmits the pupils to the exit pupil plane of the relay optical systems. In this case, it is desirable that the right, the left, and the secondary objective optical systems make exit pupils on a nearly identical pupil plane and the pupils do not overlap on the pupil plane. The plane of the exit pupils made by the objective optical systems becomes an entrance pupil plane of the relay system. If the pupils overlap on the pupil plane, it is impossible to separate the pupils completely after the relay optical system without cross-talk. Especially the cross-talk between the right and the left image is fatal for stereoscopic observation because the right image mixes the left image. Accordingly, it is desirable to take such arrangement.
Also in this case, it is desirable to have an optical means on the rear side of the relay optical system to separate the pupils made by the relay optical system.
In addition, it is desirable that the right, the left, and the secondary objective optical systems form intermediate real images in the respective objective optical systems for the same reasons as in the first rigid endoscope optical system.
Moreover, it is desirable that the left and the right objective optical system have larger lens diameter than the secondary objective optical system for the same reasons as in the first rigid endoscope optical system.